1. Technical Field
The present invention relates to an ink composition, and a recorded matter, a recording method and a recording apparatus using the ink composition.
2. Related Art
U.S. Pat. No. 4,880,465 discloses a white ink composition containing hollow resin particles as a white color material. The hollow resin particle is defined by an outer shell made of a liquid-permeable resin, having a hollow interior. The hollow interior of the hollow resin particle of the ink composition filled with a solvent, so that the specific gravity of the resin particle comes to substantially the same as that of the ink composition. Consequently, the hollow resin particles can be stably dispersed in the ink composition. If an image is formed on a recording medium with the ink composition, the solvent filling the interiors of the hollow resin particles is replaced with air by drying, and the hollow resin particle has a difference in refractive index between the outer shell and the hollow interior. This difference causes light scattering to produce a hiding power (hence, to produce white color). The outer shell of the hollow resin particle is generally formed of a transparent resin, such as acrylic resin.
Japanese Unexamined Patent Application Publication Nos. 2000-103995, 2000-239585 and 2006-56990 disclose techniques for enhancing the ejection stability and storage stability of a white ink composition or other color ink compositions. It is however desired that these techniques further be improved in terms of the printing properties.
The white ink composition may be used in combination with other color ink compositions (color ink compositions other than white color ink composition hereinafter referred to as color ink compositions). From the viewpoint of forming a white hiding layer and of the color reproducibility, the combinations of these ink compositions may be taken as follows: (i) an image is recorded by forming a white image region and a color image region on a medium; (ii) a white image layer is formed with a white ink composition, and then a color image layer is formed on the white image layer with a color ink composition; and (iii) a color image layer is formed with an color ink composition, and then a white image layer is formed on the color image layer with a white ink composition.
The present inventors have found that long-term storage and a high-humidity condition degrade the quality of images formed by combining a white ink composition containing hollow resin particles and a color ink composition. In the case of (i), the white image region becomes clear (transparent) around the boundary between the color image region and the white image region. In the cases of (ii) and (iii), the hollow particles present in an image formed by superposing the white image layer and the color image layer one on top of the other became clear to degrade the color tinge of the recorded image.